This invention relates to a pesticidal formulation containing zinc oxide and, in particular, a pesticidal formulation containing zinc oxide for use on potatoes, dry beans, and other crops. Zinc provides an essential element for plant nutrition and zinc deficiency commonly causes poor plant growth. The modes currently used to apply zinc to plants to prevent or remedy zinc deficiency are clear liquids and suspensions of a soluble zinc compound such as zinc sulfate and various zinc chelates. Zinc oxide, although cheaper than zinc sulfate, has not been generally used because of its recognized inability to efficiently enter the plant.
U.S. Pat. No. 3,130,034 to Young describes one method of overcoming zinc deficiencies. Young teaches an aqueous solution formulated by incorporating zinc sulfate in aqueous ammonia to provide a solution with a desirable salt out temperature. Unfortunately, aqueous solutions of zinc sulfates corrode milled steel and form large quantities of scale and rust in process tanks and equipment.
U.S. Pat. No. 3,620,708 to Ott teaches another method for delivery of zinc to plants. The Ott formulation consists of water, zinc oxide, phosphorous pentoxide, and ammonia to create an ammonia based solution fertilizer providing nitrogen, phosphorous and solubilized zinc.
The methods that have been used in the art to deliver zinc to plants use zinc in the form of zinc salts and chelates. Because of the high solubility of zinc salts in water, a zinc salt, such as zinc sulfate or a chelated form, delivers zinc through the roots or foliage systems of a plant. These are the preferred and accepted methods for increasing the zinc levels within a plant. One disadvantage with these forms of zinc is that they are very soluble in water and tend to wash off foliage with dew and precipitation. Furthermore, zinc salts are more difficult and expensive to formulate in combination with conventional pest control agents.
A need has developed for a method which more effectively delivers zinc to plants. A further need has developed for a delivery system which is less expensive than current systems to formulate and which will be less likely to wash off the plants in heavy precipitation.